1. Field
Disclosed herein is a current-compensated choke having a ring core and at least two coils each having the same number of windings, and a method for producing a current-compensated choke of this type.
2. Description of Related Art
Chokes are inductive components in electrical engineering and electronics, which are used among other things in the suppression of interference pulses. A very widespread subtype of suppressor chokes, for example, for suppressing interference currents that occur in the same direction in the outgoing lead and the return line, are current-compensated chokes, which are also known as “common mode chokes.” Current-compensated chokes are characterized by several, but at least two coils, which are flowed through in the opposite direction by operating current. As a result, with ideal coils, i.e., coils that are completely symmetrical to one another with the same number of windings, the same sector and the same wire guide, the magnetic fields of the coils in the core of the choke cancel one another, so that the choke has a low inductance for the operating current, while the inductance of the choke for the interference currents occurring in the same direction is high. Deviations from an ideal, completely symmetrical coil lead to losses with the increasing frequency of the operating current, which losses are to be kept as low as possible.
The design of current-compensated chokes is subject to a number of geometric and electromagnetic conditions. In order to keep the ohmic losses low, the wires used for the coil are selected to be as thick as possible. In order to achieve high inductances for interference currents in the same direction, the winding is carried out as a rule on a toroidal magnetic core, which should be as small as possible, however, because of various installation conditions. However, at the same time the individual coil should thereby comprise as many windings as possible. The galvanic isolation between the coils is also essential. Wires of the individual coils, the windings of which all have to be guided through the center hole of the toroidal magnetic core, must therefore be prevented from touching one another.
These geometric and electromagnetic conditions generally make it necessary to wind current-compensated chokes by hand or using hand operated mechanical traction devices and similar mechanical aids, e.g., crochet needles. However, it is virtually impossible to achieve exactly symmetrical coils with a manual winding technique of this type. Despite the high production expense, cross-overs between the wires of individual windings and inaccuracies in the guide of the wires can often occur.
Accordingly, there remains a need to improve the symmetry of the coils with a current-compensated choke without increasing expense.